Blake's 7 is an odd one if you want to you can laugh at the really bad special effects or you can take an opinion like the BFI that it portrays a gritty dystopian future away from the shining optimism of ST:TOS.
The first series was entirely written by Terry Nation (or at least that is what it says on the credits) and is pretty basic SF. Highlights include the only episode Douglas Camfield directed - Duel and the last two episodes Deliverance and Orac.
Series 2 becomes more quest type with the search for Star One but is let down by the swapping of Stephen Greif for Brian Croucher as Travis.
Series 3 is probably the best with a superb sequence of episodes which allow the characters to come to the fore Rumours of Death and Sarcophogus are standouts.
Series 4 has a more glossy feel and looks more like Star Wars including the design of Scorpio. It misses Jan Chappel and Glynis Barber's character is pointless but episodes like Orbit, Sand and Blake make you feel like you are watching high quality SF
I am a huge B7 fan and that is quite a balanced summary. Well done, good sir.